1. Field of the Invention
The present invention relates to a scroll member for a scroll type of fluid machinery and the scroll type of fluid machinery produced thereby, and in particular, to a scroll type of fluid machinery, which is used for a refrigeration circuit of an air conditioner mounted in a vehicle, and a scroll member used therefor.
2. Description of the Related Art
Heretofore, a scroll type of fluid machinery has two scroll members combined together. Each of the scroll members has a spiral element formed in a spiral shape around an axis and a base plate provided at an end face of this spiral element in an axial direction in one piece. With combining two scroll members, one side of scroll member is located within spiral gaps by another side of spiral element, and is contacted with another side of spiral element as well. In this manner, a closed space confining fluid between both spiral elements is formed.
One side of scroll member is fixed (hereinafter, this is called a "fixed scroll member"). In addition, although another side of scroll member performs swing motion that is near to a circle along a circular orbit, its rotation about a shaft is prevented (hereinafter, this is called a "movable scroll member").
When the scroll type of fluid machinery is operated, the movable scroll member is driven by a motor and the like. The above-mentioned closed space is carried toward the center along the spiral by relative swing motion of the movable scroll member to the fixed scroll member. In consequence, the fluid can be compressed.
Heretofore, end milling is used for machining of a wall surface of the spiral element when the scroll member is manufactured. However, since high precision is necessary in both of surface roughness and positional accuracy, productivity of spiral machining is extremely low.
Furthermore in prior art, burrs arise in circumference of a base plate surface when a part of the base plate surface that is nearer to the center than an extension line of an inner wall surface of the spiral element is finished. In the subsequent process, removal of the burrs is required. Hence, the prior art has a disadvantage of many machining processes.
Moreover in the prior art, only a base plate is machined on the extension line from the spiral end of the spiral inner wall. Therefore, the top of an end mill is worn away earlier than the side face of the end mill, and hence, tool life becomes short. This is a reason why a tooling cost increases.
On the other hand, a scroll member is disclosed in the prior art (Japanese Patent Publication (JP-B) No. 4-52842), the scroll member whose spiral element has a part of an outer wall surface that is an area from its spiral end to at most half of the circumference and has a bare surface, that is casting surface. This scroll member has a problem that burrs arise in an outer edge section, and in particular, on the boundary between an area that is left in a bare surface and a machined surface in the base plate section.
Further in the fixed scroll member that is composed of the scroll member and a casing in one piece, it should be machined with an end mill to an intake pocket section for sucking gas, and, therefore, has a disadvantage that productivity is further low, and hence, its cost increases.